This invention relates to an apparatus and a method for measuring the spatial distribution of the intensity, phase and orientation of the magnetic field generated in or around an electronic device.
The technique of measuring the spatial distribution of magnetic field in the vicinity of an electronic device is useful in locating the source of the current attributable to unwanted electromagnetic radiations (known as electromagnetic interference) or the cause of electromagnetic interference attributable to mutual interference between different electronic devices that gives rise to erroneous operations or degraded performances of the electronic devices.
The inventors of this invention have already developed such magnetic field probes, methods and apparatuses for measuring magnetic fields generated by electric and electronic devices as disclosed in the patent documents, JP-A-2002-156430 and JP-A-2003-279611, and also have made patent applications related to the probes, the measuring methods and the measuring apparatuses. Particularly, JP-A-2002-156430 relates to magnetic field probes and JP-A-2003-279611 to methods and apparatuses for measuring magnetic fields.
In general, the intensity and phase of the magnetic field in the vicinity of a measurement object are measured by using a probe element wherein the open ends of a loop-like conductor whose size is large enough to have a desired measurement resolution are connected respectively with the one end (hereafter referred to as a signal conductor) and the other end (hereafter referred to for simplicity as a ground conductor) of a pair of feeder lines. The loop-like conductor mentioned above and ones to be mentioned hereafter mean not only a circular conductor but also any one of polygonal conductors. Further, the open ends of the loop-like conductor are separated from each other. The feeder lines consist of a signal conductor and a ground (GND) conductor which are electrically connected with each other via a resistor (hereafter referred to also as a terminal resistor). The GND conductor need not be necessarily kept at the earth potential in a narrow sense, but may be electrically coupled to the reference potential of a magnetic field measuring apparatus.
When a loop-shaped conductor having such a structure as described above is placed in the vicinity of a measurement object, the magnetic field present in the vicinity of the measurement object induces a current in the loop-like conductor and a voltage is developed across the terminal resistor that terminates the feeder lines. The intensity and phase of the magnetic field in the vicinity of the loop-like conductor can be detected by measuring the magnitude and phase of the voltage developed across the terminal resistor.